1. Field of the Invention
The present invention relates generally to catheters and methods of treating the stenosis of an artery. In particular, the present invention relates to catheters and methods for puncturing, crossing and debulking chronic total occlusions (CTOs) in arteries caused by the buildup of arterial plaque tissue, and to hub assemblies used with such catheters.
2. Description of the Related Art
Chronic total occlusion (CTO) is a condition where arterial plaque tissue grows to complete stenosis of an artery and prohibits blood flow. A CTO is formed by the agglomeration of three separate physiological materials: (i) cholesterol or fat, (ii) collagen or fibrous matter, and (iii) calcium-based deposits. A CTO is also often referred to as a functional occlusion.
There are two causal pathogenic phenomena often associated with the formation of a CTO. The first is the late development of an acute occlusion. The second is the progressive occlusion of a long-term high degree stenosis. Both involve a pre-existing plaque or thrombus to which the fat and fibrous material adhere, building up until a blockage of the blood vessel occurs.
The CTO mass or CTO body, consisting of fat, fibrous matter, and calcium deposits, begins to form with fat and fibrous material attaching first. Over time the fat or cholesterol is replaced with dense collagen and calcium deposits which represents the hardened CTO body typical of this condition. The inner portion of a CTO body is softer than the distal and proximal ends which are the hardest part of a CTO body. A reduction in vessel diameter is referred to as shrinkage or negative remolding. The distal and proximal ends of a CTO are often referred to as the fibrous caps and are considered the hardest and most dense portions of a CTO.
In attempting to repair CTOs, the ability to complete a successful recanalization of a total occlusion is limited as surgeons have had difficulty crossing the CTO with a guidewire. The inability to cross a CTO with a guidewire is the principal cause of failure of the procedure to remove such blockage, as more than 50% fail for this reason. Traditional repair of a CTO proceeds through four distinct steps. First, the CTO is perforated. It is preferred that both the proximal and distal fibrous caps are perforated. Second, the lesion which gave rise to the plaque formation and ultimate CTO is debulked. Third, the blood vessel is dilated. And finally, given the high rate of reocclusion, the repaired or recanalized vessel is assisted in remaining a passable vessel by a supporting device, such as a stent.
There is a need in the industry for improved devices and methods to assist surgeons in crossing CTOs.